Over 60% of 3- to 5-year-olds in the United States attend center-based, non-relative childcare. Early caregiving experiences are integral to the development of cognitive and behavioral self-regulation capacities that undergird children?s school readiness, socio-emotional competence, and mental health. Unfortunately, recent national reports highlight exceptionally high levels of occupational and psychosocial stress in the early childhood workforce. Surprisingly little is known about the mechanisms that link these stressors to early childhood teachers? caregiving behavior or to children?s self-regulation. Our long-term goal is to develop a biofeedback intervention to ensure that children receive high-quality caregiving, thereby paving the way for positive self-regulatory outcomes. The objective of the proposed exploratory study is to lay the theoretical groundwork for this intervention by testing a model that conceptualizes emotion regulation, mindfulness, and parasympathetic tone in teachers as central resources that foster their wellbeing and capacity for sensitive, responsive caregiving. Eighty preschool teachers will complete assessments of their occupational and psychosocial stressors, rewards and supports, emotion regulation and mindfulness. Teachers? heart rate variability (HRV), a putative measure of the brain?s capacity to modulate arousal via the parasympathetic nervous system, will be recorded directly within the classroom over three workdays, concomitant with intermittent teacher ratings of negative stress and samples of salivary cortisol, a product of the hypothalamic pituitary adrenal stress response system. Teacher sensitivity and responsiveness toward students will be observed directly. The self-regulation of selected students (n~320) will be assessed via direct observation, developmentally sensitive tasks, and parent report. This study will achieve three specific aims: 1) characterize the overlap among emotion regulation, mindfulness, and parasympathetic tone in preschool teachers; 2) establish the strength of hypothesized links from occupational and psychosocial stress to teacher responsiveness and sensitivity via teachers? classroom-based parasympathetic tone; and 3) determine whether teachers? emotion regulation, mindfulness, and parasympathetic tone correlate with students' self-regulation independent of students? socio-familial experiences. The use of multi-modal assessment strategies in a sample with varying financial backgrounds as well as stringent control for student sociofamilial factors will address key limitations in the rigor of prior research. The study will fulfill an important need to understand the implications of early childhood teachers? stress and psychophysiological characteristics for children?s development. Critically, by clarifying these links, the study will establish whether a classroom-based HRV biofeedback intervention may help to alleviate stress and enhance responsiveness and sensitivity in preschool teachers. This research will advance the mission of NICHD to ensure that all children lead healthy, productive lives by delineating targets for the promotion of self-regulation capacities that are foundational to children?s wellbeing.